In transmission technology, adaptive equalizers are used to suppress the effect of analogue transmission media on transmitted signals that are recoded from their digital to the corresponding analogue form. A conversion takes place on the transmission side of the transmission system according to a given code, e.g. biphase, HDB3 etc, to adjust the signal flow to the medium. On the receiver side, recoding to the original digital form therefore takes place. The analogue signal will be distorted and delayed, due to imperfections in the medium.
It is known to transmit the data symbols on the transmitter side according to the so-called 2B1Q code. This involves zeros and ones in a data flow being recoded in pairs, e.g. so that 00 is recoded to a pulse having a given amplitude, 01 to a pulse having another amplitude etc. In addition, the pulses are transmitted such that a pulse following on a pulse is started before the former is terminated, i.e. there is an overlapping pulse flow. On the receiver side, this gives rise to a received signal, the remote signal, which comprises a main pulse preceded by a plurality of "precursors" and followed by negative and positive "postcursors", which affect subsequently received remote signal pulses.
For eliminating, or at least suppressing these precursors and postcursors it has been proposed in the prior art to use equalizers, where these include first and second digital filters, the first filter equalizing the precursors, and the second filter the postcursors, e.g. as described in "Adaptive Equalization", Proceedings of the IEEE, Vol. 73, No 9, September 1985, p. 1357.